1. Field of the Invention
This invention relates to a camera with a motor drive unit that make it possible to provide an automatic exposure setting device.
2. Description of the Prior Art
Conventional single lens reflex cameras are generally provided with an exposure control apparatus that have shutter time and diaphragm aperture adjusting rings, either of which is manually controlled in accordance with the exposure value. Recently, in the course of development of the camera art toward automatic exposure control, a variety of automatic exposure setting devices have been proposed. These proposed devices automatically adjusting either the exposure time or the diaphragm value. This adjustment is made in accordance with the exposure value determined by the preselected diaphragm value or shutter speed, respectively in combination with the available light conditions. These manual and automatic exposure setting devices have their respective merits, and it can not be said which is superior.
The use of an automatic exposure setting device in the camera, though giving an advantage in simplifying the manipulation necessary for exposure through reducing by one the number of independent manual operating steps, nevertheless necessitates a complicated control circuit with an increase in the electrical drain on the camera battery. To permit satisfactory exposure control apparatus operation without imposing a need for frequent replacement of the battery the capacity and voltage of the battery must be relatively large. Provision also must be made for battery testing and for protecting the battery from unnecessarily running down, or otherwise the chance for taking photographs often would be lost. Particularly with the exposure setting that is adapted to automatically adjust the diaphragm value as a function of a preselected shutter speed, because of the need for a spring-powered driving member that acts on the diaphragm presetting ring, it is difficult to achieve a reduction in the size of a camera that employs a device of the nature. This driving member is operatively connected to a camera reset mechanism which has a film winding lever as an operating member. In this circumstance, if the force of the drive spring is increased to assure the possibility of making snap photography, the driving torque of the film winding lever is corresponding increased.
To avoid such difficult problems, the manual exposure setting device is preferred except for the somewhat more time-consuming operation of manually adjusting the shutter time or diaphragm value in comparison with the automatic exposure setting device. This manual adjustment is carried out in accordance with an exposure value that is based on reading a display in the field of view of a camera finder. Because of this the electrical circuit this is incorporated in the camera which employs a manual exposure setting device may be made simpler than that of the camera which employs an automatic exposure setting device. Consequently, the electrical power consumption in cameras with manual exposure setting devices is decreased to a large extent. An additional advantage is that, if the adjusted combination of shutter time and diaphragm value is not suited for the contemplated photography, another combination of shutter time and diaphragm value equivalent to the desired exposure value can be provided.
By taking into account the inconsistent features of these two types of devices, it is possible to design the camera so that the manual and automatic exposure condition settings can be selectively controlled. In this case, however, the camera must be provided with a change-over device for selecting either one of the manual and automatic exposure modes. This will contribute to an increase in the complexity of construction and arrangement of the exposure control apparatus and in the size of the camera. More especially in the case of multiple-use cameras with various accessories, the addition of an independent manual operating means is quite disadvantageous in preventing the necessary manipulation from being overlooked when the camera is being readied for operation. In the course of developing a high performance camera system, it has been difficult to achieve compactness for those of the system components which are incorporated in the camera body without sacrificing the accuracy and reliability of exposure and coordination control.
Accordingly, the present invention has for its general object to provide a camera system which achieves the advantages of the conventional manual and automatic exposure setting devices.
An object of the present invention is to provide a method for setting a camera diaphragm in a camera associated with a motor drive unit in a manner that the diaphragm control mechanism is automatically operated with electrical and mechanical power supplies from the unit battery and motor respectively. With the camera detached from the motor drive unit, the diaphragm value is manually adjustable in accordance with the exposure value.
Another object of the invention is to provide a motor driven camera having selective control of the manual and automatic exposure condition settings.
These and other objects and features of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings in which: